Re: [Qemu-devel] [RFC-v2 3/6] vhost-scsi: add -vhost-scsi host device for use with tcm-vhost

[Nicholas A. Bellinger]

On Sat, 2012-08-18 at 22:12 +0300, Michael S. Tsirkin wrote:
> On Tue, Aug 14, 2012 at 01:31:14PM -0700, Nicholas A. Bellinger wrote:
> > On Mon, 2012-08-13 at 11:53 +0300, Michael S. Tsirkin wrote:
> > > On Mon, Aug 13, 2012 at 08:35:14AM +0000, Nicholas A. Bellinger wrote:
> > > > From: Stefan Hajnoczi <address@hidden>

<SNIP>

> > > > +static VHostSCSI *vhost_scsi_add(const char *id, const char *wwpn,
> > > > +                                 uint16_t tpgt)
> > > > +{
> > > > +    VHostSCSI *vs = g_malloc0(sizeof(*vs));
> > > > +    int ret;
> > > > +
> > > > +    /* TODO set up vhost-scsi device and bind to 
> > > > tcm_vhost/$wwpm/tpgt_$tpgt */
> > > > +    fprintf(stderr, "wwpn = \"%s\" tpgt = \"%u\"\n", id, tpgt);
> > > > +
> > > > +    ret = vhost_dev_init(&vs->dev, -1, "/dev/vhost-scsi", false);
> > > 
> > > This -1 is a hack. You need to support passing in fd from
> > > the monitor, and pass it here.
> > > 
> > 
> > Mmm, looking at how vhost_net_init + tap.c does this, but am not quite
> > what fd needs to be propagated up for virtio-scsi -> vhost-scsi..
> > 
> > Can you please elaborate on this one a bit more..?
> > 
> 
> The idea is to allow running as a user without access to
> /dev/vhost-scsi.
> For this, allow passing in the fd of /dev/vhost-scsi through unix domain 
> sockets.
> 

Ah, that is a pretty neat trick..   So for vhost-scsi code, this would
mean something along the lines of the following, yes..?

Thanks MST!

diff --git a/hw/vhost-scsi.c b/hw/vhost-scsi.c
index 4206a75..8af8758 100644
--- a/hw/vhost-scsi.c
+++ b/hw/vhost-scsi.c
@@ -21,6 +21,7 @@ struct VHostSCSI {
     const char *id;
     const char *wwpn;
     uint16_t tpgt;
+    int vhostfd;
     struct vhost_dev dev;
     struct vhost_virtqueue vqs[VHOST_SCSI_VQ_NUM];
     QLIST_ENTRY(VHostSCSI) list;
@@ -114,13 +115,32 @@ void vhost_scsi_stop(VHostSCSI *vs, VirtIODevice *vdev)
 }
 
 static VHostSCSI *vhost_scsi_add(const char *id, const char *wwpn,
-                                 uint16_t tpgt)
+                                 uint16_t tpgt, const char *vhostfd_str)
 {
-    VHostSCSI *vs = g_malloc0(sizeof(*vs));
+    VHostSCSI *vs;
     int ret;
 
+    vs = g_malloc0(sizeof(*vs));
+    if (!vs) {
+        error_report("vhost-scsi: unable to allocate *vs\n");
+        return NULL;
+    }
+    vs->vhostfd = -1;
+
+    if (vhostfd_str) {
+        if (!qemu_isdigit(vhostfd_str[0])) {
+            error_report("vhost-scsi: passed vhostfd value is not a digit\n");
+            return NULL;
+        }
+
+        vs->vhostfd = qemu_parse_fd(vhostfd_str);
+        if (vs->vhostfd == -1) {
+            error_report("vhost-scsi: unable to parse vs->vhostfd\n");
+            return NULL;
+        }
+    }
     /* TODO set up vhost-scsi device and bind to tcm_vhost/$wwpm/tpgt_$tpgt */
-    ret = vhost_dev_init(&vs->dev, -1, "/dev/vhost-scsi", false);
+    ret = vhost_dev_init(&vs->dev, vs->vhostfd, "/dev/vhost-scsi", false);
     if (ret < 0) {
         error_report("vhost-scsi: vhost initialization failed: %s\n",
                 strerror(-ret));
@@ -140,7 +160,7 @@ static VHostSCSI *vhost_scsi_add(const char *id, const char 
*wwpn,
 VHostSCSI *vhost_scsi_add_opts(QemuOpts *opts)
 {
     const char *id;
-    const char *wwpn;
+    const char *wwpn, *vhostfd;
     uint64_t tpgt;
 
     id = qemu_opts_id(opts);
@@ -164,6 +184,7 @@ VHostSCSI *vhost_scsi_add_opts(QemuOpts *opts)
         error_report("vhost-scsi: \"%s\" needs a 16-bit tpgt\n", id);
         return NULL;
     }
+    vhostfd = qemu_opt_get(opts, "vhostfd");
 
-    return vhost_scsi_add(id, wwpn, tpgt);
+    return vhost_scsi_add(id, wwpn, tpgt, vhostfd);
 }
diff --git a/qemu-config.c b/qemu-config.c
index 33399ea..2d4884c 100644
--- a/qemu-config.c
+++ b/qemu-config.c
@@ -636,6 +636,9 @@ QemuOptsList qemu_vhost_scsi_opts = {
         }, {
             .name = "tpgt",
             .type = QEMU_OPT_NUMBER,
+        }, {
+            .name = "vhostfd",
+            .type = QEMU_OPT_STRING,
         },
         { /* end of list */ }
     },